Abnormalities in outer segment renewal and/or cyclic nucleotide metabolism exist in rodents with hereditary retinal degeneration. Defects in these basic processes have been hypothesized to exist in other species, including man, affected with retinal degeneration. Developmental and degenerative forms of hereditary retinal degeneration are present in different breeds of dogs. In affected animals, the P.I. will determine if defective outer segment renewal and/or cyclic nucleotide metabolism are associated with the degeneration of the visual cells. Moreover, the P.I. will determine if these changes are the result of photoreceptor degeneration or cause the disease. Breeding experiments with affected dogs of different breeds will determine if single or multiple gene defects exist in dogs with hereditary retinal degeneration.